What sort of diet helps people lose more weight? Do overweight people lose more weight on a low-carbohydrate diet (like Atkins) or on a low-fat diet (like Weight Watchers and others)?
A carefully designed study published in the current issue of the Annals of Internal Medicine answers that question. The study enrolled over 300 obese adults and randomized them to a low-carbohydrate diet or a low-fat diet. Importantly, patients with diabetes, high cholesterol and high blood pressure were excluded. The low-carbohydrate diet group was instructed to restrict carbohydrates and to have as much fats and proteins as needed to feel satisfied. (This is essentially the Atkins diet.) The group randomized to a low-fat diet was instructed to limit total calories to between 1200 and 1800 kcal per day, with less than 30% of total calories from fat.
Both groups attended periodic behavioral group sessions to discuss their progress and learn skills for persevering with the diet. Both groups were also instructed to pursue an exercise program consisting largely of walking. The groups were followed for two years.
The authors’ were trying to show that a low-carbohydrate diet would lead to greater weight loss, but actually the weight loss was the same in both groups. Each group lost an average of 24 lb after one year and 15 lb (or an average of 7% of their body weight) after two years. About a third of the participants in each group had dropped out by two years.
One lesson from this study is that perseverance in any diet program will yield meaningful weight loss. It doesn’t matter which diet. The second lesson, highlighted by the large numbers of drop-outs, is that this is hard to do. So get started, and don’t quit.
Annals of Internal Medicine article: Weight and Metabolic Outcomes After 2 Years on a Low-Carbohydrate Versus Low-Fat Diet
My post in 2009 comparing different diets: Scientifically Proven Weight Loss Method: Eat Less